Microorganisms such as fungi, yeast, bacteria, and algae have ability to produce lipids. Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, phospholipids, and others. The main biological functions of lipids include energy storage, as structural components of cell membranes, and as important signaling molecules.
Lipid is generally accumulated in microbial cell. Therefor, there have been practiced a variety of methods to extract lipids from microbial cells endowed with lipid-producing ability. To release lipids from source material, it might be necessary to destruct cell walls prior to lipid extraction. The disruption may occur physically, enzymatically and/or chemically. Preferably, cell disruption is performed by mechanical means. Several methods have been used for the physical disruption of cells, including homogenization, sonication, freeze/thaw, extrusion, and mechanical grinding. However, these methods require quite a long time to recover a sufficient amount of lipids and therefore, efficient extraction cannot be performed. For example, homogenizayion of wet microbial biomass may create emulsions which make the subsequent extraction step difficult.